The present invention relates generally to integrated circuit devices such as the microprocessors of computers and more particularly to the cooling of such devices to below ambient temperatures for improved efficiency and enhanced speed of operation.
It is well known in the electronics industry that cooling integrated circuit devices to below ambient temperatures substantially improves the efficiency and speed at which such devices can operate. Such cooling is particularly beneficial in microprocessors that form the heart of modern day computers. For example, it has been found that the performance of a desktop computer can be significantly improved by cooling the microprocessor to temperatures of xe2x88x9240 degrees Centigrade or below.
Various methods and apparatus are known in the art for removing the thermal heat generated by integrated circuit devices. For example, KryoTech, Inc., the assignee of the present invention, has previously developed a refrigeration system for cooling an integrated circuit device in a desktop computer. This refrigeration system operates by circulating refrigerant fluid to a thermal head engaging the microprocessor.
The thermal head defined a flow channel through which the refrigerant fluid would pass as it circulated around the closed loop of the refrigeration system. Due to its design, the thermal head functioned as an evaporator where the refrigerant fluid was converted from liquid to gaseous form. In accordance with known thermodynamic principles, thermal energy was thus removed from the location of the microprocessor. The gaseous refrigerant drawn from the evaporator by a compressor was then fed back to a condenser where the thermal energy was removed.
As one skilled in the art will appreciate, size limitations require the refrigeration system to be relatively small with a relatively low volume of refrigerant. As a result, slight changes in ambient air temperature directly affect the system""s performance. For example, a decrease in ambient temperature causes the continuous operation fan to remove more heat from the gaseous refrigerant in the condenser. This results in liquid refrigerant exiting the condenser at a lower temperature and pressure. Given the small volume of refrigerant available, even a slight decrease in ambient temperature can reduce liquid refrigerant pressure excessively and significantly reduce the cooling capacity of the refrigeration system.
In one aspect, the present invention provides an integrated circuit device cooled by a refrigeration system. In this embodiment, the refrigeration system comprises a coolant loop containing a refrigerant, an evaporator, a compressor, and a condenser.
The evaporator is in thermal contact with the integrated circuit device and defines a flow channel for passage of the refrigerant to remove thermal energy from the integrated circuit device. The compressor increases the pressure of the refrigerant exiting the evaporator. The condenser is located between the compressor and the evaporator and includes a variable speed fan to force air across the condenser. A temperature sensor in thermal contact with the refrigerant provides a signal to a controller for varying the speed of the fan to maintain the refrigerant at a predetermined temperature.
Other aspects of the present invention provide a refrigerant system for cooling an integrated circuit device. The refrigerant system comprises a coolant loop containing refrigerant, an evaporator, a compressor, and a condenser.
The evaporator is in thermal contact with the integrated circuit device and has an inlet plenum and an exhaust plenum. The evaporator further defines a flow channel between the inlet plenum and exhaust plenum, and the refrigerant passes through the flow channel to absorb thermal energy from the integrated circuit device, changing the refrigerant to a gaseous state. The compressor has a suction and a discharge, and the coolant loop connects the evaporator exhaust plenum to the compressor suction. The gaseous refrigerant passes through the compressor and is discharged at a higher pressure. The condenser connects between the compressor discharge and the evaporator inlet plenum. The condenser includes a variable speed fan to remove thermal energy from the gaseous refrigerant passing through the condenser, changing the gaseous refrigerant to a liquid state. A temperature sensor in thermal contact with the refrigerant provides a signal to a controller for varying the speed of the fan to maintain the refrigerant at a predetermined temperature.
In some exemplary embodiments, the temperature sensor measures the temperature of the refrigerant between the condenser and the evaporator. In other exemplary embodiments, the coolant loop includes a capillary tube between the condenser and the evaporator for restricting flow of the refrigerant from the condenser to the evaporator. It will often be desirable that the capillary tube produces a refrigerant pressure entering the capillary tube of more than 225 pounds per square inch.
Still further aspects of the present invention are provided by a method used to cool an integrated circuit device. The method uses a refrigeration system to circulate a refrigerant throughout a coolant loop including a compressor, a condenser, and an evaporator. The method controls refrigerant pressure by providing a variable speed fan operational across the condenser for removing thermal energy from the refrigerant. The method detects a temperature of the refrigerant at a predetermined location and compares the temperature to a predetermined value. If the temperature exceeds the predetermined value, indicating that the refrigerant pressure is too high, the method increases the variable speed of the fan to reduce the temperature.
If the predetermined value exceeds the temperature, indicating that the refrigerant pressure is too low, the method decreases the variable speed of the fan to increase the temperature. In an exemplary embodiment, the predetermined location is between the condenser and the evaporator.
Other objects, features and aspects of the present invention are discussed in greater detail below.